Variable voltage transformer device



July 1960 G. L. OSBORNE ET AL 2,946,903

VARIABLE VOLTAGE TRANSFORMER DEVICE Filed Sept. 9, 1957 2 Sheets-Sheet l FlG.7

INVENTORS' GERALD L. OSBORNE LlLBERN A. LAWSON ATTORNEYS July 26, 1960 s. L. OSBORNE ETAL 2,

VARIABLE VOLTAGE TRANSFORMER DEVICE Filed Sept. 9, 1957 2 Sheets-Sheet 2 FlG.|l

INVENTORS GERALD L. OSBORNE LILBERN A. LAWSON ATTORNEYJ VARIABLE VOLTAGE TRANSFORMER DEVICE Gerald L. Osborne and Lilbern A. Lawson, both of 712 SE. Hawthorne Blvd, Portland, reg.; said Lawson assignor to said Osborne Filed Sept. 9, 1957, Ser. No. 682,919

4 Claims. (Cl. 307-156) This invention relates to a variable voltage transformer device and more particularly to a small compact device suitable for installation in the panelboard of an airplane for dimming instrument and panel lamps or other cockpit lights of the airplane although the device has utilility in any environment Where it is desired to provide an efficient system for providing a variable voltage from a source of constant or nearly constant voltage.

In an airplane it is desirable for the pilot to be able to adjust the level of illumination of panel and instrument lights, or other cockpit lights, to suit the ambient light conditions, as Well as the preference of the pilot. In general, prior devices for this purpose have been either a rheostat for inserting a variable amount of resistance in series with the lamp circuits or have been autotransformers having a rotary contact directly engaging the bared ends of the turns of wire on the transformer core. The rheostats referred to unnecessarily load the source of electrical power and emit objectionable heat, since they dissipate substantial amounts of energy in the form of heat. The previously employed autotransformers have been expensive and have also been unreliable as the wiping contacts on the ends of the wires cause rapid wear and this is augmented by the fact that turns of the winding of the autotransformer are repeatedly short-circuited-and the resulting heavy currents are thereafter repeatedly broken.

In accordance with the present invention, a variable voltage transformer device is provided employing a tapped autotransformer and a reactor in a circuit which provides a plurality of output voltages in steps having a greater number than the number of taps on the autotransformer and in which short circuiting of any turns of the transformer or reactor winding is eliminated, switching being accomplished by switch contacts which are separate from the windings of the autotransformer. In the preferred structure, the autotransformer and reactor are supported and clamped in the switch structure itself to provide-the co'mpact arrangement referred to above and to enable the entire assembly to be mounted in a small size casing which can be secured to or mounted upon a panelboard and which has a minimum of external connections.

An object of the present invention is therefor to provide an improved variable voltage transformer device particularly suitable for panel light dimming and analogous uses.

Another object of the invention is to provide a compact variable voltage transformer device in which a tapped autotransformer and a reactor are connected in an improved switch circuit which provides a greater number of voltage steps than the number of transformer taps and eliminates short circuiting of turns of the windings of either the reactor or transformer.

A further object of the invention is to provide a variable voltage transformer device in which an autotransformer and a reactor are supported in and clamped in a switch supporting structure so as to provide a unitary States Patent 0 assembly having a limited number of external terminals and capable of being mounted on the back of a panelboard with switch actuating mechanism extending to the front of such board.

A still further object of the invention is to provide a variable voltage transformer device in which a base mem ber and supporting columns of a rotary switch are employed to support an autotransformer and reactor in a unitary assembly providing a plurality of voltage steps.

Other objects and advantages of the invention will appear in the following description of a preferred embodiment shown in the attached drawing, of which:

Fig. 1 is a side elevation of the device of the present invention shown as being mounted on the back of a panel with the actuating shaft of the device extending through the panel;

Fig. 2 is a front elevation of the device of Fig. 1;

Fig. 3. is a rear elevation of the device of Fig. 1;

Fig. 4 is a view similar to Fig. 1 with a portion of the casing broken away and parts omitted;

Fig. 5 is a vertical section taken on the line '5-5 of Fig. 4;

Fig. 6 is a view similar to Fig. 5 taken on the line 6-6 of Fig. 4;

Fig. 7 is a view similar to Fig. 5 taken on the line 7-7 of Fig. 4;

Fig. 8 is a fragmentary section through one of the switch assembly supporting columns;

Fig. 9 is a partial vertical section taken on the line 9-9 of Fig. 6;

Fig. 10 is a view of a clamping plate employed in the, device of the present invention looking in the direcelements and contact engaging elements of the switch of the present invention; and

Fig. 12 is a diagrammatic view showing the circuit of the device of the present invention.

The device of the present invention includes a switch structure 10 in which is mounted an auto'transformer 12 and a reactor 14 and which includes a stationary switch plate 16 and a rotary switch member 18 (Fig. 5). The entire switch assembly 10 including the transformer 12 and reactor 14 is positioned within a cylindrical metal casing 20 having ventilation openings 21 and a front portion 22 closing the front end of the casing. The casing has an open rear end provided with a closure in the form of a circular switch base member 24 made of insulating material and forming part of the switch structure 10. The other elements of the switch structure 10 are supported on columns including elongated screws 26 having their heads countersunk in the outer surface of the base member 24 and extending inwardly through such member toward the front portion 22 of the casing 20. The screws 26 have spacing sleeves 28 and spacing washers. 30 thereon which in conjunction with the screws 26, fo'rm supports for the switch plate 16 and a clamping plate. 32. The entire assembly is clamped together by elongated nuts 34 upon the inner ends of the screws 26.

The base member 24 has recesses 36 and 38 (Figs. 7 and 9) formed in its inner surface for receiving the cores 40 and 42 of the transformer 12 and reactor 14, respectively, and, as shown in Figs. 9 and 10, the clamping plate 32 has lugs 44 for engaging the cores of the transformer and reactor, such cores also engaging the reinforcing rim 46 of the plate 32. The cores of the transformer and reactor are thus clamped between the clamping plate 32 and the base member 24 and held in position by the recesses 38 and 36 and the lugs 44 and rim 46. They base member 24 also has connecting lugs 48, 50 and 5.2 (Fig. 7) positioned in recesses in the inner surface of the base member 24 and which are deeper than the recesses 36 and 38. The lugs 48, 50 and 52 are held in position by terminal screws '54 extending through the base member 24 to provide for external connections to the transformer device. The lugs 48, 50 and 52' are thus positioned in recesses partially covered by the cores 40 and 4-2 and have ends extending beyond the edges of such cores to enable connection of such lugs to the circuit housed in the casing 20. Additional recesses 53 (Fig. 7) are provided for additional lugs providing for additional external connections and it is apparent that additional switch members similar to the switch plate 16 and rotary switch member 18 can be provided in a longer casing 20 to provide for other switching functions.

' The stationaryswitch plate16, Which is preferably of ceramic or other rigid insulating material, has secured to its front and rear surfaces a plurality of contact elements, thecontact elements on one surface of the switch plate being designated a, b, c, d, e and f, and the corresponding contact elementson the other surface of the plate being designated a, b, c, d, e and f (Fig. 11), respectively. The constant elements of each pair a--a', bb', etc., are connected together so as to be in effect single contact members. The switch plate also carries an additional contact element 60 on one surface and another contact element 62 on its other surface, the relative position of the various contact elements and members being best shown in the diagrammatic view of Fig. 11. The stationary switch plate has a central circular aperture in which is mounted the rotary switch member 18. The rotary switch member 18 has circular contact engaging elements 64, 65 on its opposite surfaces which overlap the periphery of the central aperture of the stationary switch plate 16 in a conventional manner to maintain the rotary switch member in position. As shown most clearly in Fig. 11, the contact engaging elements 64 and 65 have gaps 66 and 67 respectively therein to provide an off position of the switch.

The entire switch assembly thus far described is retained in the cylindrical casing 20 by a pair of screws 68 (Figs. 2 and 8) having their heads countersunk in the front portion 22 of the casing 20 and having their threaded ends received in the nuts 34. A reinforcing plate 70 is mounted in the interior of the casing 20 adjacent the end portion 22 thereof and a conventional switch actuating mechanism including a detent plate 72 is held in position against the reinforcing plate 70 of the casing 20 by the screws 68. Such switch actuating mechanism also includes a conventional rotary detent mechanism 74 at tached to a shaft 76 extending to the exterior of the casing through the reinforcing plate 70 and front portion 22. The shaft 76 is journaled in a sleeve78 secured to the detent plate 72 and also extending through the front portion 22 f the casing 26. The shaft 76 is held against endwise movement in the sleeve toward the interior of the casing by a split washer 80. The sleeve 78 extends through an aperture in a panel 82 and a nut 84 on the sleeve holds the entire variable voltage transformer device in position against a panel. A positioning lug 86 carried by the reinforcing plate 70 extends through the front portion 22 of the casing 20 into another aperture in the panel to prevent rotation of the casing 20. The shaft 76 has a portion extending inwardly of the casing through a slot in the rotary switch member 18, as shown most clearly in Fig. Rotation of the shaft 76 rotates the rotary switch member 18. The particular switch shown is a 12-position switch of which eleven positions are used and suitable conventional stops (not shown) are em ployed to stop the member'in the ofi or zero position and in the tenth position. In Figs. 11 and 12, the contact engaging members 64 and 65 are shown in the off or Zero position.

In the circuit of Fig. 12, the contact engaging members 64 and 65, as well as the positions of the various contact elements, are shown in developed form. The Winding of the jautotransformerlz has five taps, A, B, C, D and 4 The tap A is connected to contact elements a and a, and similarly the taps B, C, D and E are connected to a pair of corresponding contact elements, the contacts 1 and f being connected to one end of the winding of the autotransformer. The end terminals of the reactor 14 are connected to the contact elements 60 and 62. The reactor has a center tap which is connected to an external terminal marked LV. The two ends of the autotransformer winding are connected to the terminals marked HV and G. In the position of the switch held in Fig. 12, the contact elements 68 and 62 are in gaps in the contact engaging elements 64 and 65 so that the switch is in its off position. Upon movement of the contact engaging elements 64 and 65 one step to the right in Fig. 12, the contact engaging elements 64 and 65 engage contact members 60 and 62 to close the circuit and also engage contact elements a and b, respectively, to provide a first voltage step and upon the next step to the right, such contact engaging elements engage contact elements 17 and b, respectively, to provide the next voltage step. Upon the next step to the right, the contact engaging elemens engage contact elements 12 and c to provide the next voltage step and it will be apparent that indexing of the rotary member 18 to carry the contact engaging elements 64 and 65 from the off position through the ten on positions, will provide ten voltage steps utilizing the five taps of the winding of the autotransformer 12 the external connections G and LV flows in opposite directions in two end portions of the reactor 14 so as to produce opposite magneto motive forces. The reactor thus has low impedance for output load current but the reactor 14 provides high impedance for current flowing through the reactor between adjacent taps of the autotransfonner when the end terminals of the reactor are connected to such adjacent taps, since such current flows in the same direction through both end portions of the reactor. As a specific example, the winding of the autotransformer 12 may be energized through the terminals HV and G from a source of alternating current supplying 28 volts at 380 to 440 c.p.s. and the taps on the transformer may be arranged to provide, in ten steps, voltages of 9, 10.2, 11.5, 12.8, 14.5, 16.2, 18.5, 20.8, 24.3 and 27.8 volts, the windings of the transformer and reactor being designed to carry 4 amperes full load output current. The device of the present invention is, of course, not limited to such voltage steps nor load current, and it is to be understood that other details of the device may be varied within the scope of the following claims.

' We claim:

1. A variable voltage device comprising a unitary switch and transformer assembly including a support member, a switch operating shaft extending through said support member and journaled in said support member, a switch plate spaced axially of said shaft from said support member and having circumferentially spaced contacts, a rotary switch member rotated by said shaft and having contacts engaging said spaced contacts, a transformer supporting plate spaced axially of said shaft from said switch plate, a transformer clamping plate spaced axially of said shaft from said transformer supporting plate, 5 a transformer positioned between said supporh'ng plate and said clamping plate and having a closed iron core and a tapped winding connected to said spaced contacts, means for securing said support member to a supporting structure, and means for supporting all of said plates from said support member and for clamping said transformer between said supporting plate and said clamping plate.

2. -A variable voltage device comprising a unitary switch and transformer assembly including a support member, a switch operating shaft extending through said support member and joumaled in said support member, a switch plate spaced axially of said shaft in one direction from said'support member and having circumfer'entially.

spaced contacts, a rotary switch member rotated by said In all cases, load current between i shaft and having contacts engaging said spaced contacts,

a transformer supporting plate spaced axially of said shaft in said direction from said switch plate, a transformer clamping plate spaced axially of said shaft in said direction from said transformer supporting plate, a transformer and a reactor positioned between said supporting plate, a transformer and a reactor positioned between plate and said clamping plate, said transformer and reactor each having a closed iron core, said reactor having a winding connected to said spaced contacts and said transformer having a tapped winding connected to said spaced contacts, means for securing said support member to a supporting structure, and means for supporting all of said plates from said support member and for clamping said transformer between said supporting plate and said clamping plate.

3. A variable voltage device comprising a unitary switch and transformer assembly including a support member, a switch operating shaft extending through said support member and journaled in said support member, a switch plate spaced axially of said shaft from said support member and having circumferentially spaced contacts, a rotary switch member rotated by said shaft and having contacts engaging said spaced contacts, a transformer supporting plate spaced axially of said shaft from said switch plate, a transformer clamping plate spaced axially of said shaft from said transformer supporting plate, a transformer positioned between said supporting plate and said clamping plate and having a closed iron core and a tapped winding connected to said spaced contacts, means for securing said support member to a panel with said shaft extending through said panel, means for supporting all of said plates from said support member and for clamping said transformer between said supporting plate and said clamping plate, a casing having walls extending axially of said shaft and surrounding said assembly, said support member constituting one end of said casing and said clamping plate forming a closure for the other end of said casing and having terminals providing external electrical connections to said device.

4. A variable voltage device comprising a unitary switch and transformer assembly including a support member, a switch operating shaft extending through said support member and journaled in said support member, a switch plate spaced axially of said shaft from said support member and having circumferentially spaced contacts, a rotary switch member rotated by said shaft and having contacts engaging said spaced contacts, a transformer supporting plate spaced axially of said shaft from said switch plate, a transformer clamping plate spaced axially of said shaft from said transformer supporting plate, a transformer and a reactor position between said supporting plate and said clamping plate, said transformer and reactor each having an exposed iron core, said reactor having a winding connected to said spaced contacts and said transformer having a tapped winding connected to said spaced contacts, said supporting plate and said clamping plate each having portions receiving and fitting said cores, means for securing said support memher to a supporting structure, and means for supporting all of said plates from said support member and for clamping said transformer between said supporting plate and said clamping plate with said portions engaging said cores.

References Cited in the file of this patent UNITED STATES PATENTS 2,115,069 Hall Apr. 26, 1938 2,348,222 Olson Mar. 9, 1944 12,680,164 Lennox June 1, 1954 2,786,122 Strain Mar. 19, 1957 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noa 2 946 903 July 26 1960 Gerald Le Osborne 5119 It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5 line 7 strike out "plete a transformer and a reactor positioned between Signed and sealed this 3rd day of January 1961a SEA L) Attest:

KARL Ho AXLINE ROBERT C. WATSON I Attesting Ofiicer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noo 2 946 903 July 26 1960 Gerald La Osborne et al,

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column ES line 7 strike out "plate a transformer and a reactor positioned between 9 Signed and sealed this 3rd day of January I961a SEA L) Attest:

KARL n, AXLINE ROBERT C. WATsoN Attesting Oflicer Commissioner of Patents 

